Study: Tomatoes can turn caterpillars into cannibals

A fascinating new study by scientists at the University of Wisconsin-Madison indicates that tomatoes have a secret weapon.

That tomato plant may look like easy prey for a hungry caterpillar, just sitting there waiting to be eaten. But scientists at the University of Wisconsin-Madison have discovered that they have a secret defense mechanism that involves turning caterpillars to cannibals.

In a new paper, scientists describe a mechanism where the tomato plant releases a compound called methyl jasmonate that not only signals to other plants in the area that they are under attack, but it gives the leaves a noxious taste.

As the caterpillars become frustrated at the lack of sustenance the tomato plant is providing them, they turn on each other, researchers found. Scientists had observed both the plant’s behavior and the cannibalism by the caterpillars before, but until now hadn’t been able to put both of them together.

“It often starts with one caterpillar biting another one in the rear, which then oozes. And it goes downhill from there,” says University of Wisconsin-Madison integrated biology Professor John Orrock in a statement. Orrock is the author of the study, published in Nature Ecology & Evolution on July 10. “At the end of the day, somebody gets eaten,” he added.

Orrock and his colleague, postdoctoral researcher Brian Connolly — along with undergraduate student Anthony Kitchen — devised a set of experiments involving the beet armyworm, a type of caterpillar.

“Beet armyworms are important agricultural pests, in part because they can feed on a variety of plants,” Connolly said. “And early, influential work describing plant responses to herbivore attacks used tomato and beet armyworm. We build on that work here.”

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